https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/16.1/html/storage_guide/ch-cinder#section-volumes_advanced_encryption The storage guide currently documents use of 256 bit encryption keys. Barbican now allows us to store 512 bit keys when using aes-xts, which we should support for Cinder volumes in OSP: https://review.opendev.org/c/openstack/barbican/+/577096